Labelling machines are commonly used to transport, prepare and apply labels to containers, such as bottles, or articles of all sorts.
Particularly widespread is the use of glued labels, i.e. portions of a labelling material that are cut from a web at appropriate lengths, upon which glue is applied by gluing means (such as a gluing roller, spray and injector systems or the like) and which, finally, are transferred and applied, onto respective containers or articles.
Automated implementation of this sequence of operations emails, in practice, retaining—by suction—the strips of labelling material on the outer lateral surface of a vacuum drum, for glue application and for delivery to an output station.
A conventional vacuum drum group for use in this context comprises a vacuum drum mounted, in a rotatable manner about its axis, on a stationary distributor member.
The vacuum drum has an approximately cylindrical lobed configuration and is adapted to receive a succession of strips of labelling material at an input station and, after rotating about its axis by a given angle, to release the strips of labelling material at an output station, so that said strips can be applied to respective articles or containers.
The stationary distributor member has first air passages connected to a vacuum source; the vacuum drum is in turn provided with second air passages, which are configured to communicate with the first air passages at certain angular positions of the drum as it rotates about its axis, and end into a plurality of vacuum ports formed through an outer lateral surface of the drum for receiving the labels.
More particularly, vacuum ports are formed in a plurality of damping pads and intermediate sections which, together, define the outer lateral surface of the vacuum drum, as has been described e.g. in co-pending European patent application 13425015.8 in the name of the same applicant.
When being retained by the vacuum drum, a label shall typically have the leading end held on one pad, the trailing end held on another pad and the remaining (intermediate) part held on a section of the drum outer lateral surface comprised between the two mentioned pads.
The afore-mentioned co-pending European patent application further describes, in greater detail, how pads and intermediate sections are arranged about the periphery of a vacuum drum and how, in use, they cooperate with a strip of labelling material as it is cut off and received onto the outer lateral surface of the vacuum drum and, immediately thereafter, brought in coupling arrangement with gluing means, to finally be released off the outer lateral surface of the vacuum drum and delivered to a container. In practice, the distance between two pads is substantially equal to the length of the strip of labelling material to be processed as measured along the circumference of the drum.
Furthermore, the height of the drum is approximately equal to the height of the strip of labelling material to be processed as measured parallel to the rotation axis of the drum. In practice, the height of the drum is slightly less than the height of the strip of labelling material (label) to be processed, so that the upper and lower edges of the label overhang the vacuum drum by a few millimeters, which helps prevent glue from contaminating the vacuum drum surface.
Roll-feed labelling machines are known to be capable of operating with great efficiency and at very high speed, which is ideal for meeting the continuously increasing through-puts required on the market. In order to do so, however, roll-feed labelling machines need to rely on a continuous, gap-less supply of containers at the output station when operating at full speed. Furthermore, ramp-up mid ramp-down times are needed when starting up and shutting down, respectively, operation of the labelling machine.
These limitations can cause problems, in particular when a labelling machine is designed to be blocked into a group of processing machines each implementing a different operation in the packaging line, e.g. blow-moulding, filling and capping machines.
Those machines are constantly run at their maximum speed, whereas the labelling machine generally operates at a speed that may be lower than or, at most, as high as that of those other machines in the group.
Production constraints may generate gaps in the succession of containers reaching the labelling machine and/or impose working with an intermittent feed of the containers within the same block (e.g. due to interventions of an operator for quality checks, or the like).
This is greatly undesirable because it may easily cause a number of containers to be labelled incorrectly or labels to be released when no container is being delivered to receive it. This may entail, aside from a minor loss of labelling material, the need to discard labelled products which do not satisfy certain production requirements. On top of that, the possibility that glued labels accumulate in parts of a machine where their presence is not expected represents an even more undesirable drawback, that can be detrimental to the quality of the overall label application process and, in even more general terms, can hinder proper operation of the labelling machine as a whole.
Furthermore, while capable of operating steadily at very high speed, roll-feed labelling machines clearly need to be started up from an idle condition to reach that steady operation mode, just as they need to be shut down to go back to that idle condition. Therefore, their speed needing to be ramped up/down, problems of operative coupling/timing with the other processing machines in the group often occur. A preliminary phase of rather fine tuning of relative speeds is typically required, and this typically results in labelling material being incorrectly transferred onto containers.
The loss of some labelling material at this stage does not represent a major issue from an economic point of view. However, the need to subject a labelling machine to a major ramp acceleration or deceleration during start-up and shut down, respectively, can overstress the machine and even lead to a highly undesirable process crash.
Therefore, the need is felt in the art for a method of handling a web-like labelling material in an automated labelling process whereby it is possible to overcome at least partly the drawbacks outlined above.
In particular, the need, is felt in the art for a method of handling a web-like labelling material in an automated labelling process that makes it possible to reduce the amount of labelling material that goes to waste during start-up and shut-down of the labelling machine, as well as when, during normal operations, gaps are formed in the succession of containers to be labelled, e.g. because of issues in any other processing machine operatively associated with the labelling machine—as is generally the case in the packaging process of a pourable product.
It is, therefore, an object of the present invention to provide a method of handling a web-like labelling material in an automated labelling process, which makes it possible to meet said need in a simple and cost-effective manner.
Furthermore, it is an object of the present invention to provide a labelling machine vacuum drum for handling, accordingly, a web-like labelling material in an automated labelling process.